Daily Invader

Chesapeake Bay Crabs

European Green Crab (Carcinus maenas)


European Green Crab (Carcinus maenas) Introduced from Europe in the early 1800s (ca 1817).


The European Green Crab arrived on the Atlantic shore from Europe in the early 1800s and in Maryland and Virgina coastal bays in1874. With such a long history it’s no wonder that some sportsmen who use them as bait believe the crabs are native. Green Crabs are small, maximum body size 3 inches, and thus are no match for the larger Blue Crab (Callinectes sapidus), the heavy weight favorites in a claw-to-claw match up. For this reason Green Crabs in the Chesapeake Bay are almost never seen and have had no reported impacts. But without a larger crab to keep them at bay, Green Crabs have had serious impacts on other species like soft-shelled clams along the Gulf of Maine. Complete Record 


Chinese Mitten Crab (Eriocheir sinensis)


Chinese Mitten Crab (Eriocheir sinensis) is native to Asia and was introduced to the Atlantic Coast 2005.


The Chinese Mitten Crab is the only catadromous crab in the Atlantic. Catadromous means that they spend their adult lives in freshwater and their larval and juvenile lives in salt water; therefore you could find one of these fuzzy-clawed crabs in a freshwater stream or in your crab pot. Because mitten crabs invaded the Atlantic Coast only a few years ago, we don’t know very much about their status as an established population. But we are very concerned about them because in other areas where they have established populations they have caused both ecological and economic harm. We need your help to monitor and control the population while these crabs are still rare. If you find one, log in to Mitten Crab Watch and report your catch. Complete Record  


Japanese Shore Crab (Hemigrapsus sanguineus)


Japanese Shore Crab (Hemigrapsus sanguineus) arrived in ballast water from Asia.





Japanese Shore Crab is a small square crab that lives under rocks along the shore. These crabs are native to the western Pacific—Russia, Korea, and North China to Hong Kong, and Japan —and were likely transported as larvae in ballast water. The first collection in North America was a single ovigerous female discovered by an observant biology student on a class field trip in 1988 in Cape May County, NJ. Since then many other specimens of both sexes and varying ages have been found in Cape May Harbor, indicating that a breeding population is established there. In 1994–1996, SERC conducted surveys for the Japanese Shore Crab from Virginia Beach, VA north to Atlantic City, NJ. The crab was found throughout this range in man-made rocky intertidal habitats (jetties, bulkheads, etc.) with salinities over 20 ppt. Because these crabs are restricted to rocky habitats, which are limited in Chesapeake Bay, they are unlikely to have significant economic impacts. In much of the Northeast however, they have become extremely abundant, competing with other crab species, and feeding on mussels, snails, and other shore fauna, changing the ecology of rocky shore habitats. Complete Record 


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